I could be wrong here but I believe that DX11 is native on Win 7 and there is nothing you can do short of rolling back to Win XP.
I am running win 7 64 bit on my Office pc and an onboard gpu that I am sure does not support DX11 w/o problems. If anything, your issue is with steam or installation of the game. I know that most games, at some point, will ask you to install DX and, most people, say NO to it thinking that they already have the newest or that installing the one from the game will cause an issue.
The short answer is, NO, it won't cause an issue, but it needs to install a file or a few files to work with its own game... let it happen.
You also don't specify why you think your problem is with DX.
Oh, in my gaming rig at home I also run Win 7 ultimate 64 bit and a GTX260 video card that does not support DX11 and I have no issues whatsoever.